#include <iostream>

 #include <cstdio>

 #include <algorithm>

 using namespace std;

 int n, dp[][][][], g[][];

 int main()

 {

     int x, y, z;

     scanf("%d",&n);

     while()

     {

         scanf("%d%d%d", &x, &y, &z);

         if(x ==  && y ==  && z == )

         break;

         g[x][y] = z;

     }

     for(int i = ; i <= n; i++)

         for(int j = ; j <= n; j++)

             for(int k = ; k <= n; k++)

                 for(int l = ; l <= n; l++)

                 {

                  dp[i][j][k][l]=max(max(dp[i-][j][k-][l],dp[i-][j][k][l-]),max(dp[i][j-][k-][l],dp[i][j-][k][l-]))+g[i][j]+g[k][l];

                  if(i==k&&l==j) dp[i][j][k][l]-=g[i][j];

                 }

     printf("%d",dp[n][n][n][n]);

 }